Abstract:
The measurement of direct chlorophyll a fluorescence in photosystem II (PSII) and
the JIP test based O-J-I-P polyphasic transient analysis is becoming increasingly popular
among the techniques suitable for accessing effects of stress conditions on the photosynthetic
apparatus. In the present study, the well known effects of Methyl Viologen (MV) which is
commonly known as “Paraquat” on the photosynthetic apparatus were probed by the JIP test
in Euglena, a unicellular autotrophic organism which has a chlorophyll a/b antenna system as
it is typical of higher plants.
The cells were exposed to a series of MV doses as control, 0.1, 0.2, 1 and 2 mmol
and, immediately after the exposure; the chlorophyll fluorescence was measured using
AquaPen AP-C 100 fluorometer. The resultant O-J-I-P transients were analyzed according to
JIP-test and several functional and structural parameters were derived to explain the PSII
behavior.
